GB2219563A - Variable ratio vehicle steering gear mechanism - Google Patents

Description

1 2.2 1 ' 6 3 APPARATUS This invention relates to an im-Drovement of a sma

-anz,- -teernc aiDraratus designed for a recuced amoun-- of steering wheel operation required to steer the steered is wheels ulD to their steering angle.

Steering apparatus which is commonly used in automobiles requires more than one full turn of the steering wheel to achieve steering of the steered wheels up to their 2 0 ma...L-ii steering angle, and such steering wheel operation constitutes a factor to fatigue people, such as professional drivers, who drive cars Therefore, a small-angle steering apparatus which enables a large steering angle of the steered wheels by a small amount of operation of the steering wheel has been in demand. To meet such a requirement. the steering gear ratio may be set at a high value, as seen in formula cars. However, if the gear ratio is simply increased, steering response in the vicinity of the central position of the steering wheel becomes oversensitive and, particularly during running at a high speed, corrective steerin.,' - 1 operazion become difficult.

For such a small-angle steering apparatus, since a large angle is obtained in the steered wheels from a small. steering angle of the steering wheel, it is preferable thaz the steering force be increased as the steering angle increases, so that the steering angle will not abruptly io increase even if the apparatus is carelessly operated by a driver -;.; ho is accustomed to an ordinary steering system. Howe--er, if' a small- angle steering apparatus is to be achieved simply by increasing the steering gear ratio, since the steering force is almc,st constant with respect to changes in steering angle, it is liable to cause excessively sharp steering, which constitutes a safety problem. If the steering force is set high to prevent such sharp steer-ing, the steering force in the vicinity of the central position of the steering wheel also increases, which tends to increase the driver's fatigue.

With a view to overcoming such problems of steering apparatus, it is anaim of the present invention to provide a small-angle steering apparatus having characteristics such that the steering response and steering force increase as the steering wheel operation angle increases.

2 In accorciance with the invention there is provided a small-angle steering apparatus comprising a variable ratio gear mechanism disposed in a steering force transmission 1Dassage for transmitting rotation of a steering wheel to a steering gear bo...., the.- ariable ratio gear mechanism comprising a -first crear connected -,, the szeering wheel side having e-'-"eczJve radius 2:raduall-- increasing with increasing steering., angle is and a second gear connected to the steering box side having effective radius gradually decreasing with increasing steering angle, the s.-,a-L.Iesr--radius portion wS zhe -4'-irsi -ea-, encraa:.,-iw r_he araes7::-radius portion of the second c-ear -.-,iien --ne steerinw wheel, is ac its central r)osit-,c;n.

Thus, the invention uses the variable ratio gear mechanism comprising the first gear having effective radius gradually increasing with increasing steering angle and the second gear having effective radius gradually decreasing with increasing steering angle to obtain increasing gear ratio with increasing angle of the steering wheel, thereby preventing the steering response from becoming oversensitive in the vicinity of the central position of the steering wheel and reducing the required amount of steering wheel operation up to the angle l_ne szeereci wneels.

Therefore, by virtue c4X' zie variable ratio gear mechanism, the above gear ratio variation characteristics are obtained, and the steering force increases with increasing steering angle, thereby preventing abrupt steering of the steered wheels even with careless manipulation by the driver.

-ear mechanism using a pair of elliptical gears can used as the variable ratio gear mechanism to give the above characteristics with a simple structure. Furthermore, with the present invention, a boosting -ear mechanism to boost the output of the variable ratio mechanism can be disposed between the variable ratio gear mechanism and the steering box to allow conventional steering boxes and power-steering systems to be used in constructions accordincr to the invention therebv reducincT produczlon costs of the steering systeirs.

Furthermore, the present invention may preferably include counter-force mechanism disposed in the steering force transmission passage to increase the rotational resistance of the steering force transmission passage in response to increasing steering angle and/or vehicle speed, which optimizes the steering force characteristics with respect to steering angle while setting an optimal gear ratio by the 4 --ariab-e ratio 5ear mechanism, thereby providinE ontimai steering -force characteristics according to -,ne vehicle 5 sr,eed ranze. Other features and advantages c-A' the invention will become obvious from the following descr:-=-Jon rI -he r;rezferread e-nocc-i:-.ents, reference being made to the accompanvincr xawinas -n wnacn:

Figgs.1 to -7 relate to a first embodiment of the present invention. Fi=c,.! is a schematic vertical sectionai view of the apparatus. Fi-d-2 a schematic plan view of an elliptical.crear mechanism. Fi.g.3 is a schematic plan view of a counter-force mechanism. Fig.4 is a graph showing steerin.g angle characteristics. Figg.5 is a diagram showing steerin-g force characteristics. Figs.6 to 8 relate to a second embodiment of the present invention. Fig.6 is a schematic vertical sectional view of the apparatus. Fig.7 is a schematic view showing structure of a hydraulic pressure supply device. Fig.8 is a graph showing steering force characteristics vs. vehicle speed. Fig.9 is a schematic vertical sectional view of a third embodiment of the present invention. Fig.10 is a schematic vertical sectional view of a fourth embodiment of the present invention.

Preferred embodiments of the present invention will now be descr-zed in ae-_a_i with reference to the drawin.-s.

Fgs.- --c 5 reiaze T-o a first emoodiment of the device 5 accorainz, to the --resent invention. Fig.1 is a schematic vertical sectional view showing part of the device.

Referring to Fig.!, the bottom end of a steering shaft 1 connected to the steering wheel (not shown) side is serration-connected to the tolD end of an inT)ut shaft 3 of an 14 4cal -aear mechanism 2.

el A first elliptical gear -1 of -he eill, _4 L 1)Zical gear mechanism 2, at the inside of a-casing 15 5, is unrotatably mounted on the outer periphery of the inpu-z. shaft 33, and the input shaft 3 is offset in the ma.jcr axiai direction from the center of the first elliptical gear I A second elliptical gear 6 engaging with the first elii-Dtical gear 4 in the casing 5 is unrotatably mounted on the outer periphery of an output shaft 7 disposed parallel to the input shaft 3 in the casing 5. The output shaft 7, as for the case of the input shaft 3, is disposed at a position offset in the major axial direction from the center of the first elliptical gear 4. As shown in Fig.2, in the elliptical gear mechanism 2, with the central position of the steering wheel (not shown), the smallest-radius portion of the first elliptical gear 4 engages with the largest-radius portion of the second elliptical gear 6. Thus, as the rotation of the input shaft 3 increases with increasing angle of the steering wheel, gear ratio of the =::rear -iec.nan-,sm increases. Since. in --h-s embodiment, the steering angle of zne s-,eer-,nz anz-,e is set zo about a half turn (180 degrees), the gear ratio will not decrease at a large steering angle.

As shown in Fig.1, the output shaft 7 of the elliptical gear mechanism 2 is connected to an inner valve 9 of a Dower 10 steering device through a planetary gear mechanism 8. At -he out-Dut shaft 7 is integra-.-'y formed a the lower end of t t.

planetary gear carrier 10 for the planetary gear mechanism 8, and a plurality of planetary gears 11 are rotatably supported on the planetary gear carrier 10. A ring gear -,1 of the planetary gear mechanism 8 is fixed to the casing and always engages with the planetary gears 11. A sun gear 12 of the of the planetary gear mechanism 8 is fixed to the outer periphery of the top end of the inner valve 9 and always engages with the planetary gears 11.

The planetary gear mechanism 8 acts as a speed increasing mechanism to increase the rotation of the output shaft 7 and transmit it to the inner valve shaft 9. Thus, by transmitting the axial rotation component in addition to the orbital rotation component of the planetary gears 11 to the sun gear 12, rotational speed of the sun gear 12 is increased. As a result, the steering angle response set by the elliptical gear mechanism 2 is amplified and then inputted to the power steering mechanism.

ther with an outer valve 1,13 Lhe inner valve 9, toge disposed on the out-er periphery, forms a known rotary valve. A steering output shaft 1,4 connected to the lower end of the outer valve 13 is connected to the inner valve 8 through a torsion bar 15. -A pinion gear 16 disposed on the lower outer periphery of the steering output shaft 14 engages with a rack trear 18 provided on a steering rod 17, forming a s t e e r i n g g e a r b o 9 ne- arrar.we-zienT: connecting the --, ruier-,-a-, e 9 to the power steering device and the steering gear is box 19 is known in the art, and thus will not be described further in detail.

Oorce mechanism 20 provided on the input A counter-f will now be described. A cam body 21 formed shaft integrally with the first elliptical gear 4 is disposed beneath the first elliptical gear 4 and is rotated integrally with the input shaft 3. A roller 22 urged by a spring force is pressed against the cam surface formed on the outer periphery of the cam body 21, thus acting as a pressing element.

A spring housing 23 is disposed in the casing 5, with its axial line in the direction perpendicular to the axial line of the input shaft, and two coil springs 24 and 25 having different spring constants are disposed in the spring housing 23. A counter-force piston 26 is slidably disposed in the spring housing 23, and is urged towards the input 8 25. A roiiier supporzin5 shaft - b,- the cc-11 --prings 241 and oiate 27 which is Lormed 4 ntezraiiv with the counter-f'orce piston 26 is disposed protrudingly from the inner end of the spring housing 23, and is provided at its front end with a supporting shaft 428 disposed parallel to the input shaft 1), A resin-made roller 222 is rotatably supported on the supporting shaft 23, and is pressed against the cam body 21 by the-force from the springs 24 and As shown 4r. F9.3, the cam body.1 is formed in a heart-like shaDe, and its shaft center is offset to the recess of the heart-shaped cam surface. The cam body 21 is disposed so that, with the steering wheel (not shown) at its central position, the recess which is the smallest-radius portion of the heart-shaped cam surface comes in contact against the roller 1 22. Therefore, the effective radius of the portion in contact with the roller 22 increases as the input shaft turns wi'%.h increasing steering angle. Since the maxj=xr, rotation of the input shaft 3 is set to about a half turn, the effective radius of the cam body 21 will not considerably decrease at large steering angles.

Now, functions of this embodiment will be described.

Steering input from the steering wheel is transmitted to the planetary gear mechanism 8 via the first elliptical gear 4, the second elliptical gear 6, and the output shaft 7 and, after being amplified by the planetary gear mechanism 8, is transm-lz--eci,c --he steering gear box 19. Since, in the il elli-otial gear mechanism 2, the smallest-radius norzion o-.:' the first elliptical gear 4 engages with the largest-radius portion of the second elliptical gear 6, the gear ratio of the elliptical gear mechanism 2 increases as the turning of the input shaft 3 increases. Thus, as can be easily seen from the steering angle characteristics of this embodiment shown in Fi--.4, with the steering wheel in the vicinit-y ol its central position, initial response of the steered wheels is almost the same as that of conventional art apparatus, but the response of the steered wheels becomes quicker as the steering angle increases, i.e. the steering gear ratio gradually increases with increasing steering angle. With such steering angle characteristics, the nlaxj_mlz-,. steering angle can be remarkably decreased to about a half turn.

In the counter-force mechanism 20, since the effective radius of the portion of the roller 22 contacting against the cam body 21 increases as the input shaft rotates, the springs are gradually contracted. This causes the force of the springs 24 and 25 acting on the roller 22 through the counter-f orce piston to increase wj:th the rotation of the input shaft 3 (cam body 21) so that the pressing force of the roller 22 against the cam body 21 increases with the rotation of the input shaft. As a result, the rotational resistance of the input shaft 3 increases with increasing sr-eer--i.. angle, and the steerJnz force to G-Derate the steering wheelIncreases with increasing steering angle.

-or the cases Fig.5 shows steering' force characteristics with or without the counter- force mechanism 9.0. Referring to Fig.5, even without the counterforce mechanism 20, an ncrease in the steerinc force with increasin., steerin.cr angle is obtained due to changes in ggear ratio cf the gear mechanism, but. this embodiment using the counter-f-orce mec-an-Jsm generalll--,- provides increased is steering force, which canattract- the driver's attention and, s-inc:e the difference in steering force between the central steering position and the irs=w,, steering angle position becomes greater, excessive steering angle can be prevented even with careless operation of the driver. As can be seen from Fig.5, when the steering wheel is turned back, the counter-force mechanism 20 acts to decrease the steering force, thereby facilitating the turning-back operation of the steering wheel.

Since the cam body 21, with the steering wheel at the central position, is disposed so that the recess which is the smallest-radius portion of the heart-shaped cam surface comes against the roller 22, the central position of the steering wheel is clearly defined, assistina the driver to feel the central position.

The steering force characteristics with the counter-force meenanism 20 snown in Fi.---,m.5 iss on-.,v an example, and the spring, constant of the springs and the 5 shape of the cam o-1 -he counter-force mechanism 20 can be changed to change the steering force characteristics, for example, to increase the difference in steering force between the central position and the nl=-xir= steering angle position, or to increase the initial steering force from the central Dosition.

-'z can also be seen from Fig.5, since the basic chara---er-Jstics to increase the steering force with increasing steering angle can be obtained only with the ellipzical gear mechanism 41, a minimal performance is guaranteed even with the counter-force mechanism 20 removed.

With the first embodiment, which is provided with the counter-force mechanism 20, steering force characteristics can be set independently of the steering force characteristics obtained wlth the elliptical gear mechanism 2, and steering force characteristics can be corrected to optimal ones by- setting the counter-force mechanism 20, while obtaining optimal steering angle characteristics by setting of the elliptical gear mechanism 2. This prevents the steering response from becoming oversensitive in the vicinity of the central position and, while preventing abrupt steering caused by careless steering operation, improves the operation workability of the steering apparatus - 12 reeduced steering operation ang-le up -c tne maxima-, steering an.aie.

Since the output of the elliptical gear mechanism amniified by the planetary gear mechanism 8 and then inputted to the power steering device, the maximal rotational angle inputted to the power steering device can be set nearly equal to that of conventionally used power steering devices even with the reduced rra= steering angle of the steering wheel, and conventional power steering devices can be used as they are. This enables a low-cost, simple- structured small-ang-le steering apparatus with power steering function.- Furthermore, by virtue of the central positioning function of the counter-force mechanism 20, the central position of the steering wheel is easily felt and, since an automatic centering function is achieved, steering operation such as turning-back is facilitated, with improved stability of the vehicle during straight running.

In addition, since the basic characteristics to increase the steering force with increasing steering angle can be obtained even only with the elliptical gear mechanism 2, a minimal performance is guaranteed even if a malfunction occurs in the counter-force mechanism, thereby providing improved safety.

Figs.6 to 8 relate to a second embodiment of the present Invention. In the second embodimen-1, substantial..-,.- same components as in the above first embodiment are 5 ndicateci using the same reference numbers and symbols, and detailed description for the same is omitted. in this second embodiment, the positions of the input shaft 3 and the output shaft 7 are the reverse of the first embodimen--, the input shaft 3 being disposed coaxially with the -zzee---Jnz output shaft l-11. Thus, in place of the planetary gear mechanism 8 in the first embodiment, a large-diameter he-!ica-l gear 31 connected to the iniDut shaft and a small-diameter heliGal gear 32 connected to the input valve 9 are used. In this embodiment, these helical gears 1 3.1 and -324 comprise a speed-increase mechanism. Rotation of the output shaft 7 is increased by the helical gears 31 and 321, and then inputted to the input valve 9.

In addition to the counter-force mechanism, there is provided a spring 35 for steering force adjustment. The spring 35 is disposed around the input shaft 3 and between the input shaft 3 and the easing 5. The spring is elastically deformed by the rotation of the input shaft 3 to increase its urging force and, in turn, the rotational resistance of the input shaft 3. Therefore, the spring 35 alone has almost the same effect as the counter-force mechanism 33 of the first embodiment. z A counter-force mechanism 34 has a cam body 21, which has almost the same shape as one used in the first embodiment, mounted on the output shaft 71, and a roller 5 cont-acts the cam body 21. A substantial difference from the counterforce mechanism 20 of the first embodiment is that the force exerting on the roller 222 pressing the cam body 21 is not a spring force, but a -his purpose, a plunger 36 is siidably hydraulic force. For t disposed in the perpendicular direction to the output shaft 7 in the casing 5, and the roiller 22 is rotatably supported on the front end of the plunger 36. Hydraulic pressure supplied from an in-put port 37 disposed in the casing 5 is applied to the rear end of the plunger 36. The force of the roller 22 pressing the cam body 21 varies with the hydraulic pressure inputted. Since the cam body has the same shape as in the first embodiment, the steering force increases with increasing steering angle, as in the case of the first embodLment, as lona as a hydraulic pressure is supplied from the input port 37.

Fig.7 is a schematic view showing a generating mechanism for hydraulic pressure supplied from the input port 37. An oil pump 42, which sucks hydraulic oil from a reserve tank 41 and discharges-it, is driven by a speed meter driven gear provided on a transmission output shaft. Thus, the oil pump 42 rotates in response to the vehicle speed, and the pump discharge increases with increasing vehicle sDeed. A discnarge --oorz of the oil pump 42 is connected to the input port 37 through an oil passage 43. The ois passage 43 is connected with an oil passage 44 which is connected to the reserve tank 41, and the oil passage 44 is provided with an orifice 45. Due to a flow resistance of the or-4fice 45, a hydraulic pressure in response to the flow rate is generated at the upstream side of the orifice 45 and, since the oi'L pump 112 discharges hydraulic oil in amoun.s according to the vehicle speed, the hydraulic 15pressure increases in response to the vehicle speed. Thus, 37 is applied with a hydraulic pressure the input port according to the vehicle speed.. A relief valve 46 is to return part of hydraulic oil discharged when flow rate of the oil pump exceeds a predetermined value to the reserve tank 41, thereby preventing the input port 37 from being applied with excessive hydraulic pressure.

Functions of the second embodiment will now be described. In particular in the counter-force mechanism 34, since the hydraulic pressure inputted to the input port 37 varies in response to the vehicle speed, the force of the 30roller 22 pressing the cam body 21 increases with increasing vehicle speed. As a result, rotational resistance of the input shaft increases with the vehicle speed and, as shown in Fig.8, vehicle-speed-sensitive steering characteristics are obtained in which the steering force increasing with venicle speed. Furthermore since 'Cv,-1r-.,-ie the -hape of the cam body 21, as for the case of tne first embodiment, the steering force increases with increasing steering angle, while running at a high speed where a high hydraulic pressure is supplied, the steered wheels will not be operated excessively by careless steering operation, so far as the steering wheel is not operated with a very large steering force, thus providing further improved safety. Of course the steering wheel centering effect is obtaixied, as for the case of the first embodiment.

During low-speed running of the vehicle, there is almost no control over the steering force by the counter-force mechanism 34, but by the function of the sT)rina and steerina characteristics can be set so that the steering force increases with increasing steering angle, independently of setting of the elliptical gear mechanism 2.

With the second embodiment, in addition to the same effects as obtained with the first embodiment, since characteristics to increase the steering force with increasing vehicle speed, which is preferable for a steering apparatus, can be obtained, it is possible to obtain a good steering feeling during high-speed running of the vehicle, and abrupt steering by careless operation is more positively prevented.

Furthermore, since, as in the case of conventional art steer--ng apparatus, the input shaft 33 anc. the steering out-out shaft 14 are disposed in line on the same axis, the apparatus of this embodiment can be equipped in place of conventional steering apparatus without modifying the vehicle body. Thus, the apparatus of this embodiment can be easily used interchangeably with conventional types according to the specifications of the vehicle, thus blng a wide range of applications.

enao--i--.9 is a schematic view of a third embodiment of the presen-invention, which is a modification of the above ftrs-c enbodiinent in that -= hvdraulic chamber 52 is formed between the bottom of the spring housing 23 and a spring retainer 51. In this third embodiment, hydraulic pressure in response to the vehicle speed can be introduced from the input port 37 to obtain the same vehicle speed feeling as with the second embodiment.

Fig.10 is a schematic vertical sectional view showing part of a fourth embodiment of the steering apparatus according to the present invention.

Referring to Fig.10, an elliptical gear 63 is mounted with a key 64 on a first intermediate shaft 62 which is a first shaft rotatably driven by a steering wheel 61, and an elliptical gear 66 engaging with the elliptical gear 63 is mounted with a key 67 on a second intermediate shaft 65 which is a second shaft arrancred rotatably to drive a steering gear is (not shown). When tne steering wheel, is zurned, the f-Jrs7- intermediate sha.-'E't rotates, and the rotatIon is transmitted 5 to the second intermediate shaft 65 throu01h the pair of elliptical gears 63 and 66 to drive the steering gear, changing the angle of steered wheels (not shown).

Phases of the gears 63 and 66 relative to the shafts 64 and 65 are set so that, when the angle of the steered wheels is zero, that iss, when the relative rotational positions of the first intermediate shaft 62 and the second intermediate is shaft 65 are to run the vehicle straight, the smallestradius portion of the elliptical gear 63 mounted on the first intermediate shaft 62 engages with the lar_gest-radius portion of the elliptical gear 66. This is the same as in the case of the first embodiment.

Therefore, by connecting the first and second intermediate shafts 62 and 65 through such elliptical gears 63 and 66, it becomes possible to vary the steering gear characteristics according to the steering angle, as in the case of the above second embodiment. Thus, since, in the vicinity of zero steering angle, the smallest-radius portion of the elliptical gear 63 of the first intermediate shaft 62 engages with the largest-radius portion of the elliptical gear 66 of the second intermediate shaft 65, rotation of the first intermediate shaft 62 is reduced and then transmitted to the second intermediate shaft 65. As a result, a state o- a substantially low steering gear ratio is obtained, thereby ensurinc safety during straight running of the vehicle. on the other hand, the reduction rate is gradually decreased as the steering angle increases and, halfway, turns to increase the rotation. When the elliptical gears 63 and 66. turn 180 degrees from the zero steering angle point, the largest-radius portion of the elli-.tiCal gear_63 of the first intermediate shaft 62 is engages with the smallest-radius portion of the elliptical -'rmediate shaft 65, and rotation of gear 66 of the second intt-the first intermediate shaft 65 is most increased and then transmitted to the second intermediate shaft 65. This condition corresponds to that with a high steerng gear ratio, which is possible to facilitate steering operation requiring large steering angle, for example, when putting the vehicle into a garage. Towards this end, as in the case of the previous embodiments, the fourth embodiment also enables steering angle characteristics in which the steering gear ratio increases with increasing steering angle.

Furthermore, with the gear ratio characteristics, the steering force increases with increasing steering angle, which prevents abrupt steering of the steered wheels due to careless operation of the steering wheel.

Fig.10 shows an example in which an unrotary portion is provided at the center of the steering wheel 61, where such instruments as a s-reed meter and various switches can be disposed. Referring to Fig. 10, a hollow steering shaft 70 is rotatably supported concentrically on the outer periphery of a hollow shaft 69 fixed on a steering column casing 68, and the steering wheel 61 is mounted at one end of the steering shaft 70. A device mounting plate 7l positioned at the center of the steering wheel 61 is mounted at one end of the hollow shaft 69.

A drive gear 72 is mounted on the steering shaft 70, and the drive -&ear 722 engages with an adjacent driven gear 74 mounted on a driven shaft 73 which is supported on the casing 68. The driven shaft 73 is connected to the first 2 through a universal joint 75.

intermediate shaft 6 Therefore, when the steering wheel 61 is turned, the steering shaft 70 rotates, the driven shaft 73 is rotated through the gears 72 and 74, the rotation is transmitted to rotate the first intermediate shaft 62 through the universal joint.75.

Furthermore, as described above, the second intermediate shaft 65 which is connected to the first intermediate shaft 66 through the elliptical gears 63 and 66 is connected to an output shaft 771 through a speed-increase gear unit 76. Since the output shaft 77 is connected to the steering gear through a connecting shaft (not shown), the angle of the steered wheels is varied as the output shaft 77 rotates. Numeral 78 indicates an electric tilt drive device to adjus, the tilt.

ang-Le of the steering wheel 61. 5 Although not shown, the device mounting plate 71 on the fixed hollow shaft 69 can be mounted with such instruments as a speed metery switches and other devices, which can be wired through the hollow part of the fixed shaft 69.

When instruments are disposed at the center of the steering wheel 61, if the steering wheel 61 is shaDed, for example, to a small-sized semicircular form and the maximal rotational angle of the steering wheel 61 is limited within a range of requiring no shifting of hands, for example, within 180 degrees, visibility of the instruments will not be hindered bY the driver's hands during operation of the steering wheel 61. In this case, the elliptical gears 63 and 66 of th.e present invention can be used to good-advantage to obtain good steering gear characteristics.

In the embodiment shown in Fig.10, the rotational ratio between the steering wheel 61 and the first intermediate shaft is 1:1, however, the elliptical gear 63 may alternatively be mounted on a shaft which increases or reduces the rotation of the steering wheel 61.

Furthermore, the above embodiment shows application of the elliptical gear mechanism as a variable ratio gear mechanism, however, it should be easily understood that mechanisms of other shapes can be used alternatively.

- 22 ilaims i. A small-ang-le steering apparatus comprising a variable ratio gear mechanism disposed in a steering force transmission passage for transmitting rotation of a steering wheel to a steering gear box, said variable ratio gear mechanism comprising a first gear connected to said steering 10 wheel side having effective radius gradually increasing with increasing steering angle and a second gear connected to said steering box side having effective radius gradually is decreasing with -increasing, steering angle, the s=all est -radius Do=on of: said -1i--s-i aear enaacrina with the -arcrest-radius por---,on or said second gear whe-n sald steerinc wheel is ac its central iDosition.

Claims (1)

1. 2. The small-angle steering apparatus as claimed in Claim 1, wherein said

   variable ratio gear mechanism is an elliptical -gear mechanism comprising a pair of elliptical 25 gears.

   3. The small-angle steering apparatus as claimed in Claim 1 or Claim 2, further comprisincj a speed-increase mechanism disposed 30 between said variable ratio gear mechanism and said steering gear box for increasing speed of the output of said variable ratio gear mechanism. 35 n Claim The small-ang-le steering apparatus as claimed 3, wherein said speed- increase mechanism is disposed between said variable ratio gear mechanism and a power steering mechanism.

   5. The small-angle steering apparatus as claimed in any precedincr claim, wherein a counter-force mechanism for increasing rotational resistance of said steering force transmission passage with increasing steering angle is disposed in said is steering force transmission passage.

   6. The small-angle steering apparatus as claimed in Claim c), wherein said counter-force mechanism has a cam body rotating with said variable ratio gear mechanism and a pressing element urged by urging means and_pressed against the surface of said cam body, the effective radius of the portion of said cam body contacting against said pressing element being minimal -when said steering wheel is at its central position and increasing with increasing steering angle.

   7. The small-angle steering apparatus as claimed in Claim 1, further comprising a counter-force mechanism disposed in said steering force transmission passage for increasing rotational resistance of said steering force transmission nassazz-- with increasinr vehicle sr)eed.

   8. The smal-l-ang-le steering apparatus as c-,aimed in Claim 3, wherein said variable ratio gear mechanism transmits rotation of a first shaft connected to the steering wheel side to a second shaft, and said speed-increase mechanism 10 transmits rotation of said second shaft to a third shaft connected to the steering gear box side, said first shaft and said third shaft being disposed on the same axial line.

   9. The small-angie steering apparatus as claimed in Claim 1, wherein instruments mounted on an unrotary member are disposed at the center of said steering wheel.

   10. The small-angle steering apparatus as claimed in any Precedina I-laim, wherein the maximum steering angle of said steering wheel is set to about 180 deqrees.

   11. A small-angle steering apparatus generally as herein described, with reference to and as illustrated in the accompanying drawings.

   Publishe coS9 at The Patent Office. State House. 66 - High Hoiborn. London WCIR 4Tr.F_ Further cc-:)!c-.-I inky be ot:,.7: ne: fro.-_ nrie Pa:ertoffioe &_cn Branch, St Mary Cray. OrpingwiL Kent BR5 3P.D. Printed by Multiplex techniques Ad. St M&U Czay. Kent, Con V87